One of the most delightful moments in Mozart comes at the very end of his Symphony No. 39 in E-flat, the first of his last trio of great symphonies. It’s a piece that keeps shifting direction, from its piercing slow introduction to a flowing slow movement that turns suddenly dramatic to an enchanting wind serenade in the middle of the minuet to its teasing, high spirited finale, which suddenly just stops. That last little surprise, maybe a tribute to Haydn’s many surprises, didn’t happen when Spanish maestro Rafael Frühbeck de Burgos, one of the Boston Symphony Orchestra’s favorite guests, led it at a concert two weeks ago celebrating Mozart’s 250th birthday. In those final bars, he slowed down; instead of Mozart’s breathtaking joke, we got something emphatic, prolonged, and rounded off — something one might have heard a century ago.

Frühbeck’s expansive, consistently slow tempos smoothed out the symphony’s many contrasts. He even reverted to the pre–James Levine seating plan (first and second violins together on his left; violas, cellos, and basses on his right), which gives the orchestra a richer, thicker, but less differentiated sound, playing down the contrasts (often in the form of a dialogue) between first and second violins. I’m not categorically against this old-fashioned style, which you’ll find on some masterful “historic” recordings of classical music. But I missed something I always look forward to.

The liveliest part of the enchanting Serenata notturna (“Evening Serenade”), which opened the program, was the buoyant timpani of Timothy Genis. In the quartet of solo string players, the violins (Tamara Smirnova and Haldan Martinson) rather overpowered the viola (Steven Ansell) and the bass (Edwin Barker). The piece depends on a charm this weighty, efficient version lacked.

The audience perked up with the appearance of Gil Shaham in Mozart’s most popular violin concerto, No. 5 in A, with its “Turkish” interlude in the final minuet, an irresistible passage bursting with a brio less evident anywhere else in the concert. Shaham combined suavity and exuberance, and unfussy energy. But he too seemed to be playing in the style of an earlier generation.

Easter weekend, Frühbeck was back in a piece that demands old-fashioned grandeur: the Berlioz Requiem, which the BSO last played when Seiji Ozawa substituted it on a program shortly after 9/11. Here Frühbeck was right on target. His unforced, spacious tempos gave the Requiem a sense of inwardness, of heartfelt lament, a dignity I hadn’t heard in recent BSO performances. Berlioz depicts the Day of Judgment with four brass choirs, two of which Frühbeck deployed on opposite sides of the stage, the other two on opposing sides of the first balcony, right next to the proscenium. It was stereo rather than the usual SuroundSound but, according to an e-mail from Tanglewood Festival Chorus member Stephen Owades, closer to what Berlioz actually requests in his score (“at the four corners of the main body of singers and instrumentalists”). Still, those brass blasts shook the hall. And the soul.